In the oil and gas production industry, it is common practice to perform one or more “in-situ” tests of a hydrocarbon containing or other formation using a logging probe operating within an exploration or production well. In some circumstances, these in-situ tests include one or more NMR measurements of the formation, including the rock and the fluid contained therein. Such measurements are useful in determining a T1 value (the so-called “longitudinal relaxation time”) and a T2 value (the so-called “transverse relaxation time”) associated with the formation (e.g., the rock and fluids within the rock) and a diffusion coefficient From T1, T2 and the diffusion coefficient, a wealth of information can be obtained about physical properties of the formation.
It is also common practice to take, while the exploration or production well is being drilled, one or more cylindrical core samples of the formation and to subsequently perform one or more laboratory tests with a core sample in a laboratory. In some circumstances, these laboratory tests include NMR measurements of the core sample. Measurements in the laboratory need to be representative of the in-situ measurements. Correct (i.e., representative) data are used to optimize and establish a recovery factor for the field. In particular, greater optimization of the recovery factor for certain enhanced oil recovery (EOR) processes is possible if representative laboratory data are available.
However, a gap exists between laboratory NMR measurements and in-situ NMR measurements because experimental apparatus for performing laboratory NMR measurements on a core sample are unable to reproduce reservoir conditions experienced by the in-situ logging probe during in-situ NMR measurements. In particular, a problem with core sample holder assemblies (e.g., laboratory assemblies) for NMR measurements is that they are not able to maintain the core sample at elevated temperature and pressure while NMR measurements are being taken.
Therefore, it is an objective of the present disclosure to provide a core holder assembly and core testing method, which provide a solution to these problems.